The quartet is among several music stars who have begun recording a new version of Eric Clapton's somber 1992 hit, "Tears in Heaven," to help raise money for survivors of last month's devastating earthquake-induced tsunami in Southeast Asia that killed upward of 178,000 people.

First up was "Sad Songs" singer John, who recorded his part Thursday night in London. Pop-tenor Andrea Bocelli is scheduled to make his contribution on Friday. He'll be followed by Collins, who will lay down his track from his home in Switzerland, while Ozzy and daughter Kelly will record their take in Los Angeles.

Other artists contributing vocals for the all-star remake include Gwen Stefani, Pink, Josh Groban, Aerosmith frontman Steven Tyler, and even Robert Downey Jr. Other stars rumored to be participating include Velvet Revolver and Robbie Williams.

The charity single was dreamed up by Sharon Osbourne and American Idol's Simon Cowell, who wanted to do something to benefit the victims and the massive reconstruction currently under way.

The original "Tears" was penned by Clapton following the death of his infant son, Conor, who fell from a New York City apartment building in 1991.

Proceeds raised from the new version will go to Save the Children Fund, a tsunami-aid organization already operating in the region. A release date has not yet been scheduled.

"Tears in Heaven" isn't the only charity tune in the works. Boy George, former Bee Gees Robin and Barry Gibb, Steve Winwood and ex-Rolling Stones bassist Bill Wyman are putting the wraps on their own single, "Grief Never Grows Old."

Clapton, meanwhile, is involved in his own tsunami-related fundraiser, having agreed to perform at a Live Aid-style charity concert set to be held at Millennium Stadium in Cardiff, Wales, this Saturday and Sunday.

There's still no word whether U2 and Coldplay will play the show, which has sold more than 40,000 tickets. At last report, promoters were in talks with both groups to participate. Already on the bill: the Darkness, Elton John and Franz Ferdinand, along with U.K. rockers Feeder and singers Lemar, Katherine Jenkins and Aled Jones.

Other musicians have also stepped up. Sting, who had to scrap a Feb. 9 concert in Sri Lanka because of the catastrophe, has pledged to give 100 percent of the net profits from his Feb. 10 concert in Perth, Australia, to tsunami recovery. Queen guitarist Brian May donated the proceeds from the 1,000th London performance of the Queen-based musical We Will Rock You on Jan. 12 to the Disaster Emergency Committee. Paul McCartney kicked in nearly $2 million to the International Rescue Committee, Hilary Duff pledged a portion of profits from her sold-out Most Wanted Tour to the United Nations. Celine Dion and Björk are also doing music-related projects for UNICEF, while Incubus and Linkin Park are contributing to the American Red Cross.

And much closer to the disaster area, MTV is putting together a massive concert of its own in Bangkok that will air on its cable channels worldwide, including MTV2 in the U.S., on Feb. 3.

The MTV Asia Aid Benefit will feature live sets from Alicia Keys, Kelly Clarkson, Good Charlotte, Hoobastank and Simple Plan, as well a prerecorded performance contributed by Jennifer Lopez who's unable to attend. Proceeds from that concert, which will also include some of Asia's biggest music stars, will be given to UNICEF and local charities.

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